Buffalo thorn (Ziziphus mucronata)

Present distribution

Scientific name:	Ziziphus mucronata Willd.
Common name(s):	buffalo thorn

This weed is not known to be naturalised in Victoria

Habitat:

Recorded in open woodland, often in alluvial soils along rivers (Palgrave, 1977); Open scrubland, woodland, forest margins (WAC, 2006); Pasture (Wells et al, 1986); Forests (not usual), open scrub, rocky koppies, grassveld, bushveld & woodland, forest margins and streambanks (Palmer & Pitman, 1972); Open grasslands, dambos, and adjacent cultivated fields, heavily grazed dry scrub, thicket woodland dominated by scattered tall trees, seasonal stream forest dominated by Sorindeia to seasonally waterlogged grassland, lowland forest with mixed vines and bushes, semi-closed thicket (GBIF, 2006).

Potential distribution

Potential distribution produced from CLIMATE modelling refined by applying suitable landuse and vegetation type overlays with CMA boundaries

Map Overlays Used

Land Use:
Broadacre cropping; pasture Irrigation.

Broad vegetation types
Heathy woodland; lowland forest; swamp scrub; box ironbark forest; inland slopes woodland; sedge rich woodland; dry foothills forest; moist foothills forest; grassland; plains grassy woodland; valley grassy forest; riverine grassy woodland; riparian forest; rainshadow woodland.

Colours indicate possibility of Ziziphus mucronata infesting these areas.

In the non-coloured areas the plant is unlikely to establish as the climate, soil or landuse is not presently suitable.

map showing the potential distribution of buffalo thorn

Red= Very high	Orange = Medium
Yellow = High	Green = Likely

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Obstructs access (Csurhes & Edwards, 1998). Can be planted for use as an impenetrable hedge until the crown lifts from the ground at about 10 years (WAC, 2006); forms dense thickets on brackish flats near waterways (Van Wyk, 1972). Major impediment to access waterways.	H	MH
2. Reduce tourism?	This deciduous or semi-deciduous (Ward, 1980) shrub or small tree (Fors, 2002) would be very obvious to most visitors and would have a major impact on recreation, such as swimming in waterways.	H	MH
3. Injurious to people?	Has strong sharp thorns (Fors, 2002) to 2cm long (WAC, 2006). “The tree often ‘casts’ off small green twigs complete with thorns…causing…painful experience to barefoot strollers” (Van Wyk, 1972).	H	MH
4. Damage to cultural sites?	“The root system is not aggressive” (WAC, 2006). The ability to form dense thickets (Van Wyk, 1972) could cause moderate visual effect at cultural sites.	ML	MH
Abiotic
5. Impact flow?	Grows in alluvial soils along rivers (Palgrave, 1977) but “the root system is not aggressive” (WAC, 2006), so unlikely to impact on flow.	L	MH
6. Impact water quality?	Grows in alluvial soils along rivers (Palgrave, 1977) but unlikely to impact on water quality.	L	MH
7. Increase soil erosion?	Has been suggested for rehabilitation of sand dunes in South Africa (Griffiths & Lawes, 2006), suggesting that it has the capacity to reduce erosion.	L	MH
8. Reduce biomass?	This tree species can displace grasses (Csurhes & Edwards, 1998), which would increase biomass.	L	MH
9. Change fire regime?	Unknown	M	L
Community Habitat
10. Impact on composition (a) high value EVC	Potential distribution of Ziziphus mucronata excludes Victoria. No impact on EVCs in Victoria.	L	H
(b) medium value EVC	Potential distribution of Ziziphus mucronata excludes Victoria. No impact on EVCs in Victoria.	L	H
(c) low value EVC	Potential distribution of Ziziphus mucronata excludes Victoria. No impact on EVCs in Victoria.	L	H
11. Impact on structure?	Competes with riparian vegetation and displaces grasses (Csurhes & Edwards, 1998). Grows to 9m tall (WAC, 2006). Abundant and dominant on the flood-plain in its native range (Zietsman et al, 1989). Major effect on ground layer vegetation.	MH	MH
12. Effect on threatened flora?	The potential for Ziziphus mucronata to establish and naturalise in Victoria is highly unlikely due to ecoclimatic limitations. No impact on threatened flora in Victoria.	L	H
Fauna
13. Effect on threatened fauna?	The potential for Ziziphus mucronata to establish and naturalise in Victoria is highly unlikely due to ecoclimatic limitations. No impact on threatened fauna in Victoria.	L	H
14. Effect on non-threatened fauna?	This species forms dense thickets (Van Wyk, 1972), and can displace grasses (Wells et al, 1986), which may reduce food availability for grazing animals.	ML	MH
15. Benefits fauna?	Browse species in Zimbabwe (Dube & Ndlovu, 1996). May provide fodder for browsing animals, especially during drought (Palgrave, 1977).	MH	MH
16. Injurious to fauna?	Has strong sharp thorns (Fors, 2002) to 2cm long, and is palatable to animals (WAC, 2006). Potential for thorns to cause injury to browsing animals.	H	MH
Pest Animal
17. Food source to pests?	Seeds eaten by rodents (Fors, 2002). Fruit eaten by wild animals (Fors, 20020), including birds (Griffiths & Laws, 2006).” Leaves and fallen fruits are browsed on by stock and game and can provide useful fodder in times of drought;” fruits often remain of the tree over winter (Palgrave, 1977). May provide some food to rodents and pest birds.	ML	MH
18. Provides harbour?	Of the many studies that describe the uses of this tree by animals (Maier et al, 2006; Fors, 2002), use as habitat is never described. The deciduous nature of this tree (Wells et al, 1986) may reduce its harbour value.	L	MH
Agriculture
19. Impact yield?	Pastoral weed of South Africa (Csurhes & Edwards, 1998); out competes pastoral grasses (Wells et al, 1986); browse species in Zimbabwe (Dube & Ndlovu, 1996), with high nutritional value (Van Wyk, 1972). The deciduous nature of this tree (Wells et al, 1986) may reduce its fodder value, as it can out compete pasture, but would provide a source of fodder only when in leaf.	ML	MH
20. Impact quality?	Recorded as a seed contaminant (Wells et al, 1986), however, as a tree, it is unlikely to have much impact on harvested seed.	L	L
21. Affect land value?	No evidence that this weed affects land value.	L	L
22. Change land use?	No evidence that this weed causes changes in land use.	L	L
23. Increase harvest costs?	No evidence that this weed increases harvest costs.	L	L
24. Disease host/vector?	No evidence that this weed acts as a host for agricultural diseases.	L	L

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	Seed experiences dormancy (Hassen et al, 2005), and scarification, as would occur in avian gut passage, aids faster emergence, but is not required for germination to occur (Griffiths & Laws, 2006). High temperatures required to stimulate germination (Csurhes & Edwards, 1998). “germination is completely inhibited while the seeds are still enclosed in the fruits” (Zietsman & Botha, 1987). Requires removal of fruit for germination. This may occur over time as fruit breaks down. Requires seasonal temperatures.	MH	H
2. Establishment requirements?	Grow in full sun (Page & Olds, 1999). Requires access to light.	ML	M
3. How much disturbance is required?	Occurs along rivers, drainage lines and flood plains (Csurhes & Edwards, 1998). Highly disturbed natural ecosystems.	Ml	MH
Growth/Competitive
4. Life form?	Deciduous or semi-deciduous (Ward, 1980) shrub or small tree (Fors, 2002).	L	MH
5. Allelopathic properties?	No information.	M	L
6. Tolerates herb pressure?	Young trees must be protected from browsing cattle (WAC, 2006). Simulated browsing reduced the number of flowers and fruits (Rokke, 1998). Able to reproduce under moderate herbivory.	MH	MH
7. Normal growth rate?	Fast-growing (WAC, 2006)	H	MH
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Most abundant in dry areas & occurs in coastal regions (Fors, 2002). Resistant to frost and drought & tolerates seasonal waterlogging, salt spray and soil salinity (WAC, 2006). Rapid recovery and vigorous resprouting was observed after fire damage (Maier et al, 2006). High fire and salinity tolerance and some also of frost, drought and waterlogging.	MH	MH
Reproduction
9. Reproductive system	Hermaphroditic flowers, grows from root suckers (WAC, 2006). Flowers go through a male phase, followed by a female phase (dichogamy) (Zietsman et al, 1989), rendering them anatomically outcrossing.	H	MH
10. Number of propagules produced?	Unknown	M	L
11. Propagule longevity?	Unknown	M	L
12. Reproductive period?	Trees can produce fruit every year (Zietsman et al, 1989). Trees live for more than 10 years (WAC, 2006). Trees smaller than 2m were observed not to fruit in one study (Zietsman et al, 1989). As a fast-growing tree that can reach 4-6m in 4-5 years (WAC, 2006), would expect a 2m tree to be about 2 years old. Would expect trees to be able to produce fruit for ten years or more.	H	MH
13. Time to reproductive maturity?	Trees smaller than 2m were observed not to fruit in one study (Zietsman et al, 1989). As a fast-growing tree that can reach 4-6m in 4-5 years (WAC, 2006), would expect a 2m tree to be about 2 years old. Reaches reproductive maturity in 2-5 years.	ML	MH
Dispersal
14. Number of mechanisms?	Fruit eaten by wild animals (Fors, 2002), including birds (Griffiths & Laws, 2006) and dispersed along drainage lines after flash floods (Zietsman & Botha, 1987).	H	H
15. How far do they disperse?	Bird dispersal (Griffiths & Laws, 2006) has the potential to often move propagules at least 1km.	H	H

References

Csurhes, S. & Edwards, R. 1998 Potential Environmental Weeds in Australia, Queensland Department of Natural Resources, Brisbane. Zouhar, K. 2003, Tamarix spp. Fire Effects Information System, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, viewed: 24/10/2006, http://www.fs.fed.us/database/feis/

Dube JS & Ndlovu LR 1996, ‘A note on seasonal variations in the chemical composition of four browse species in the Matopos redsoil thornveld,’Zimbabwe Journal of Agricultural Research, vol. 32(2), pp. 179-182.

Fors, L. 2002, ‘Tree Seed Survival across a Miombo Woodland Fragmentation Gradient in Tanzania,’ Master Thesis, Arbetsgruppen för Tropisk Ekologi Minor Field Study 80 Committee of Tropical Ecology Uppsala University, Sweden http://www.env-impact.geo.uu.se/80Fors.pdf.

Griffiths, M.E. & Laws, M.J. 2006, ‘Scarification and maternal plant effects on seedling emergence in Ziziphus mucronata (Rhamnaceae),’ Afr. J. Ecol., vol. 44, pp. 273–276.

Hassen, A. Rethman, N.F.G. & van Niekerk, W.A. 2005, ‘Effect of different seed treatment options on dormancy breaking, germination and emergence of Ziziphus mucronata (buffalo thorn) seed,’ Tropical Grasslands, Vol. 39(2), p. 124-128.

Maier, W. Khoza, T. Harmse, H. Wingfield, B.D. & Wingfield, M.J. 2006, ‘A disease epidemic on Zizyphus mucronata in the Kruger National Park caused by Coniductyum chevalieri,’ studies in Mycology, vol. 55, p. 279-288.

Page, S. & Olds, M. (eds.) 1999, Botannica, Random House, Australia.

Palgrave, K.C. 1977 Trees of Southern Africa, C. Struik Publishers, Cape Town, Johannesburg.

Palmer, E. & Pitman, N. 1972, Trees of Southern Africa, Balkema, Cape Town.

Rooke T 1998, ‘Responses to simulated browsing in five savanna shrubs,’ Minor Field Studies – International Office, Swedish University of Agricultural Sciences, vol. 48.

Van Wyk, P. 1972, Trees of the Kruger National Park, Volume 2, Purnell, Cape Town, Johannesburg, London.

Wells, M.J. Balsinhas, A.A. Joffe, H. Engelbrecht, V.M. Harding, G. & Stirton, C.H. 1986, ‘A catalogue of problem plants in southern Africa incorporating the National weed list of southern Africa, Memoirs of the Botanical Survey of South Africa, vol. 53. P. 548.

Ward, CJ 1980, ‘The plant ecology of the Isipingo Beach area, natal, South Africa,’ Memoirs of the botanical survey of South Africa, no. 45.

World Agroforestry Centre (WAC) 2006, ‘Agroforestry Tree Database- Ziziphus mucronata,’ viewed: 24/10/2006, http://www.worldagroforestrycentre.org/sea/Products/AFDbases/AF/asp/SpeciesInfo.asp?SpID=1725

Zietsman, P.C. van Wyk, A.E. & Botha, F.C. 1989, ‘Vegetative and reproductive phenology of Ziziphus mucronata subsp. mucronata (Rhamnaceae),’ South African Journal of Botany, vol. 55(6), p. 564-573.

Zietsman, P.C. and Botha, EC. 1987, ‘Seed germination of Ziziphus mucronata subsp. mucronata,’ South African Journal of Botany, Vol. 53(5), p. 341-344.

Global present distribution data references

Global Biodiversity Information Facility (GBIF) 2006, Global biodiversity information facility: Prototype data portal, viewed 26/11/2006, http://www.gbif.org/

Missouri Botanical Gardens (MBG) 2006, w³TROPICOS, Missouri Botanical Gardens Database, viewed: 26/11/2006, http://mobot.mobot.org/W3T/Search/vast.html

Royal Botanic Gardens (RBG) 2006, Flora Zambesiaca, Royal Botanic Gardens, Kew, UK, viewed 13/12/2006, http://www.kew.org/efloras/search.do

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